A biological constituent concentration measuring device for determining the blood glucose non-invasively by the infrared radiation that has come from an organism (e.g., an eardrum among other things) has been proposed. For example, Patent Document No. 1 discloses an apparatus for measuring a blood glucose level in a human body tissue by making a non-invasive analysis on a radiation spectral line, which is characteristic of the human body tissue and included in the infrared radiation that has been emitted naturally as heat from his or her eardrum.
According to the Planck radiation formula, however, the intensity of the infrared radiation emitted as thermal radiation from an object varies with the temperature of the object that produces the infrared radiation. The temperature of the eardrum changes with the body temperature. For that reason, the eardrum temperature could change from one person to another or every time the measurement is done. Due to such a variation in eardrum temperature, the blood glucose levels that have been measured based on the infrared radiation emitted by the eardrum may also vary.
That is why it has been proposed that such an apparatus for measuring the blood glucose level non-invasively using the infrared radiation emitted by the eardrum should correct the influence of the eardrum temperature on the infrared radiation given out from the eardrum. For example, Patent Document No. 2 discloses a technique for correcting the influence of the temperature on the radiation spectral line by measuring the temperature inside the acoustic foramen. More specifically, the ear temperature is detected by measuring the intensity of the infrared radiation in a broad wavelength range of 8 μm to 14 μm.                Patent Document No. 1: U.S. Pat. No. 5,666,956 (its entire description and all drawings)        Patent Document No. 2: United States Patent Application Publication Ser. No. 2005/0043630 (its entire description and all drawings)        